Process of reducing fine-grained iron-containing material by means of solid carbonaceous reducing agents

Abstract

Disclosed is a process for the production of reduced iron oxide-containing materials. Iron oxide and solid carbonaceous reducing agent are charged into a first expanded fluidized bed, which is supplied with an oxygen-containing fluidizing gas. The gas residence time selected is controlled in the reactor containing the first fluidized bed so that the reduction potential will result in a reduction of the iron oxide material not in excess of the FeO stage. A gas-solids suspension discharged from the first fluidized bed is supplied to a second expanded fluidized bed, which is supplied with a strongly reducing fluidizing gas. Strongly reducing gas and a major portion of the resulting devolatilized carbonaceous material are discharged from the upper portion of the second fluidized bed. Reduced material having a metallization of 50 to 80% and the remaining devolatilized carbonaceous material are discharged from the lower portion of the second fluidized bed.

We claim: 
     
       1. A process for the direct reduction of iron oxide-containing materials, comprising: introducing an iron oxide-containing material and a solid carbonaceous reducing agent into a first expanded fluidized bed;   introducing an oxygen containing gas into said first expanded fluidized bed as fluidizing gas;   maintaining weakly reducing conditions in said first expanded fluidized bed and adjusting the gas residence time therein so that reduction potential will result as a reduction of the iron oxide-containing material not in excess of the FeO state;   discharging a gas-solids suspension from the first expanded fluidized bed;   introducing the gas-solids suspension into a second expanded fluidized bed;   supplying a strongly reducing gas as fluidizing gas into said second expanded fluidized bed;   discharging at least a portion of the devolatilized material with the strongly reducing gas from an upper section of the second expanded fluidized bed;   and discharging the reduced material from the lower portion of the second expanded fluidized bed.   
     
     
       2. The process of claim 1 wherein the reduced material has a metallization of 50 to 80%. 
     
     
       3. The process of claim 1 wherein a major portion of the devolatilized carbonaceous material is discharged from the upper section of the second expanded fluidized bed. 
     
     
       4. The process of claim 3 wherein at least a portion of the devolatilized carbonaceous material is separated from the gas and is recycled to the first fluidized bed. 
     
     
       5. The process of claim 4 wherein the gas contains CO 2  and at least a portion of the gas is purified and treated to remove CO 2 . 
     
     
       6. The process of claim 5 wherein the purified and treated gas is recycled to the second expanded fluidized bed as fluidizing gas. 
     
     
       7. The process of claim 1 wherein a portion of the devolatilized carbonaceous material is discharged from a lower section of the second expanded fluidized bed. 
     
     
       8. The process of claim 4 wherein the rate of recycle of the separated discharged carbonaceous material is a multiple of the feed rate of the iron oxide-containing material to the first expanded fluidized bed. 
     
     
       9. The process of claim 1 wherein the gas-solids suspension of the first expanded fluidized bed has a heat content which supplies the heat demand in the second expanded fluidized bed. 
     
     
       10. The process of claim 1 wherein the temperature of the suspension entering, the second fluidized bed exceeds by 30° to 80° C. the temperature of the strongly reducing gas. 
     
     
       11. The process of claim 8 wherein the multiple is 10 to 50 times. 
     
     
       12. The process of claim 7 wherein the devolatilized carbonaceous material is separated from the material which is discharged from the lower portion of the second expanded fluidized bed and at least part of the thus separated carbonaceous material is recycled to the first expanded fluidized bed. 
     
     
       13. The process of claim 1 wherein the iron oxide-containing material is preheated by the strongly reducing gas from the second expanded fluidized bed before the iron oxide-containing material is charged to the first expanded fluidized bed. 
     
     
       14. The process of claim 1 wherein the reduced material is completely reduced and smelted in at least one smelting reactor. 
     
     
       15. The process of claim 14 wherein the smelting reactor provides an exhaust gas which is used as the strongly reducing gas in the second expanded fluidized bed. 
     
     
       16. The process of claim 7 wherein a portion of the devolatilized material which has been separated from the material withdrawn from the lower portion of the second expanded fluidized bed is charged to the smelting reactor.